Laser lithotripsy for treatment of canine uroliths.

OBJECTIVE

To confirm in vivo optimal laser energy settings previously determined in vitro for lithotripsy, to develop a technique for Ho:YAG laser lithotripsy, and to evaluate acute and chronic tissue effects of laser lithotripsy.

STUDY DESIGN

Prospective, randomized preclinical trial.

ANIMALS OR SAMPLE POPULATION

Nineteen intact, adult male dogs.

METHODS

Via cystotomy, a single urolith was inserted into the urethra to the level of the base of the os penis to simulate obstruction. Uroliths (calcium oxalate, urate, or magnesium ammonium phosphate) were fragmented by Ho:YAG laser, in contact mode through a 320 micro optic fiber, passed through the operating channel of a 2.8 mm flexible endoscope. The time and total energy to fragmentation were recorded. Dogs were euthanatized immediately after lithotripsy (3 dogs) or at 3 days (7 dogs), and urethral lesions and any stone remnants were evaluated. Urethral integrity was also evaluated in 9 other dogs by endoscopy on day 10; these were also monitored clinically for 30 days.

RESULTS

The mean time for adequate fragmentation was 166.7 seconds (range, 47-494.5 seconds). The mean+/-SD energy used was 1418+/-851.2 J. In part 1, 2 dogs were obstructed with urolith fragments at necropsy. Eight dogs had minimal (<30 mg) or no urolith material evident within the urethra. Four dogs had gross focal or circumferential erosion, ulceration, or hemorrhage of the urethral mucosa. Lesions were not associated with the site of laser irradiation in 2 dogs. In dogs observed for 30 days, hematuria, pollakiuria, and stranguria that were observed after lithotripsy, resolved in all affected dogs by day 5. No mucosal lesions were observed by endoscopy and none of the dogs became obstructed.

CONCLUSION

Laser lithotripsy with the Ho:YAG laser in contact mode successfully fragmented obstructive uroliths in male dogs.

CLINICAL RELEVANCE

Laser lithotripsy may be a clinically relevant technique for treatment of urolithiasis in male dogs; clinical studies to evaluate long-term effects on urethral mucosa and the role of repeat treatment for recurrence are indicated.